This invention relates to a motor vehicle seat belt retractor and particularly to a retractor which can be operated either in emergency locking or automatic locking modes.
Most motor vehicles are equipped with seat belt systems which, when used, restrain the occupants when the vehicle is subject to high rates of deceleration which may occur during a collision. Many seat belt retractor designs are of the so-called emergency locking type. These retractors employ an inertia sensitive actuator which prevents seat belt webbing from being withdrawn from the retractor when the vehicle is sujected to decleration forces above a predetermined level, thereby restraining the vehicle occupant. During normal conditions, however, the seat belt webbing may be freely withdrawn from the retractor, providing the occupants with freedom of movement.
Another type of seat belt retractor is often referred to as an automatic locking retractor. These retractors act as a one-way clutch in that once withdrawal of the belt webbing is stopped, further withdrawal of the webbing is prevented. When, however, the seat belt is unfastened and the webbing is fully retracted within the retractor, the webbing can again be withdrawn to the desired extent. These types of retractors firmly restrain the occupant since webbing cannot be withdrawn and therefore restrict freedom of movement of the occupant.
The emergency locking retractor design has many advantages in terms of occupant comfort and convenience since they permit free movement of the occupants until the vehicle is subjected to deceleration forces above a predetermined level. Emergency locking retractors have ben found undesirable, however, when they are used to fasten a child restraint system within the vehicle. For this application, it is preferred that the seat belt system firmly and securely anchor the child restraint system to the vehicle. Since automatic locking retractors do not permit free withdrawal of webbing, they are preferable for restraining child restraint systems. In addition, certain segments of the public experience a lack of confidence as to the operation integrity of seat belt retraction mechanisms of the emergency locking type.
Due to the conflicting needs of providing adult occupant comfort and convenience, and securely fastening child restraint systems within vehicles, it is desirable to provide a dual mode seat belt retractor which may be converted between emergency locking and automatic locking operating modes in accordance with the needs of the user. It is therefore a principal object of this invention to provide such a dual mode seat belt retractor. It is a further object of this invention to provide a dual mode retractor which is easily switched between operational modes. It is yet another object of this invention to provide a dual mode seat belt retractor which is simple in design and inexpensive to produce.
In U.S. Pat. No. 4,555,075, entitled "Dual Mode Seat Belt Retractor Assembly", and assigned to the assignee of this application, a retractor fulfilling the above-described objects is disclosed. That retractor design, however, has somewhat limited adaptability to various motor vehicle designs and retractor placements since the inertia sensitive pendulum is mounted near the center of the retractor, rather than at either end thereof. The placement of the pendulum is restricted for that design since the emergency and automatic mode switching mechanism is attached to one end of the retractor, and the retractor rewind spring is connected to the other end of the retractor. Furthermore, the retractor according to the above-cited U.S. Patent is not easily adapted for seat belt webbings having various lengths since the number of rotations of the retractor spool between the points at which the operating mode is switched is relatively difficult to adjust. It is therefore another object of this invention to provide a dual mode retractor which provides greater flexibility in the mounting location of the inertia sensitive pendulum actuator, and further, one that enables the retractor to accommodate various lengths of belt webbing without major modifications.
The above objects of this invention are provided by a retractor design with includes a mechamism positioned at one end of the retractor for switching the retractor between operational modes. The mode switching mechanism includes a drive gear which causes a ring gear to rotate with rotation of the retractor spool. Extending tabs are provided on the ring gear which interact with a mode switching lever which, in one position, biases a locking bar into engagement with toothed sprockets of the spool such that the retractor operates as an automatic locking retractor. When the mode switching lever moves to another position, it disengages the locking bar so that the retractor functions as an emergency locking retactor. The retractor rewind spring assembly is preferably stacked directly on the housing which encloses the mode switching mechanism. Accordingly, a retractor is provided having one opened end which can be used to mount the inertia sensitive pendulum and associated components. The retractor according to this invention is easily modified to accommodate various webbing lengths merely by changing the point at which the ring gear tabs protrude from the ring gear.